In this page there is a link to flappybird.py at github.com. It is linked to the examples/flappybird/flappybird.py in master branch. The linked code is too new for the latest released pygamezero 1.2 and causes name not defined error for 'storage' because storage.py had introduced after 1.2 release.
The tutorial document "Migrating from Scratch" https://pygame-zero.readthedocs.io/en/stable/from-scratch.html https://github.com/lordmauve/pgzero/commits/master/doc/from-scratch.rst
In this page there is a link to flappybird.py at github.com. It is linked to the examples/flappybird/flappybird.py in master branch. The linked code is too new for the latest released pygamezero 1.2 and causes name not defined error for 'storage' because storage.py had introduced after 1.2 release.
The link on the tutorial page should be linked to the 1.2release branch. https://github.com/lordmauve/pgzero/raw/1.2release/examples/flappybird/flappybird.py